2007 Brake Problems

Hi,

My 2007 Rav4 has a very spongy brake pedal and also goes almost to the floor when braking. I've brought it to 3 different shops, one of them a Toyota dealer. The dealer says I need a brake booster and quoted $1300+ for the job. The two other shops disagree with the dealer's diagnosis and between the two of them, they installed new brake pads on all 4 wheels and turned all four rotors, power bled the system, and adjusted and greased the calipers. After all these repairs, the brakes are still spongy and very low. I'm afraid to even drive the car. Has anyone had similar brake issues? If so, what was the problem?

Please help.

I didn't find the right solution from the Internet.

References:-
http://www.rav4world.com/forums/99-4...-problems.html
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Thanks!